Can't read GPIO pins. ofxGPIO does not compile

Hi. RaspberryPi B, 512MB, 800Mhz, minibian.

I've coppied folder oxfGPIO to openFrameworks/addons
then

cd openFrameworks/addons/ofxGPIO/example-read-write
make

...and i got this:

../../../addons/ofxGPIO/src/smbus.cpp: In function ‘__s32 i2c_smbus_write_quick(int, __u8)’:
../../../addons/ofxGPIO/src/smbus.cpp:36:62: error: ‘NULL’ was not declared in this scope
     return i2c_smbus_access(file, value, 0, I2C_SMBUS_QUICK, NULL);
                                                              ^
../../../addons/ofxGPIO/src/smbus.cpp: In function ‘__s32 i2c_smbus_write_byte(int, __u8)’:
../../../addons/ofxGPIO/src/smbus.cpp:54:33: error: ‘NULL’ was not declared in this scope
                 I2C_SMBUS_BYTE, NULL);
                                 ^
../../../addons/ofxGPIO/src/smbus.cpp: In function ‘__s32 i2c_smbus_write_quick(int, __u8)’:
../../../addons/ofxGPIO/src/smbus.cpp:37:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
../../../addons/ofxGPIO/src/smbus.cpp: In function ‘__s32 i2c_smbus_write_byte(int, __u8)’:
../../../addons/ofxGPIO/src/smbus.cpp:55:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
../../../libs/openFrameworksCompiled/project/makefileCommon/compile.project.mk:335: recipe for target '../../../addons/obj/linuxarmv6l/Release/ofxGPIO/src/smbus.o' failed
make[1]: *** [../../../addons/obj/linuxarmv6l/Release/ofxGPIO/src/smbus.o] Error 1
make[1]: Leaving directory '/root/openFrameworks/addons/ofxGPIO/example-read-write'
../../../libs/openFrameworksCompiled/project/makefileCommon/compile.project.mk:126: recipe for target 'Release' failed
make: *** [Release] Error 2